Treating synthetic fibers with acetylenic glycols



TREATING SYNTHETIC FIBERS wrrn ACETYL- ENIC GLYCOLS ,Thomas C. Spence,Yorktown, Va., and Stanley A. Murdock, Concord, Califl, assignors to TheDow Chemi= cal Company, Midland, Micln, a corporation of Delaware NoDrawing. Application April 16, 1958 Serial No. 728,787

12 Claims. (Cl. 117-1383) The present invention contributes to theman-made synthetic textile fiber art. It has reference to improvementsin the manufacture of certain varieties of fibers of the type that arebased essentially upon acrylonitrile polymers and which are wet spun inand with aqueous saline systems to form intermediate aquagel filamentarystructures which, in the final stages of manufacture, are irreversiblydried to provide the desired, characteristically hydrophobic textilefiber product. The present invention relates more particularly to thetreatment of such aquagels with specific varieties of opening agents toprevent filamentary bonding, sticking and adhesion during their dryingfrom the highly hydrated aquagel state to their finished textile fiberform.

In the wet spinning of acrylonitrile polymer fibers, it is usuallyconvenient and expedient to form the fibers in continuous or endlessfilamentary lengths that are assembled in contiguous relationship duringtheir manufacture as multiple filament strands or gatherings. Quitefrequently, the filaments are handled during and subsequent to spinningin. multiple filament arrays or arrangements in which a considerableplurality of individual, component continuous filaments are in closelyassociated, substantially or ostensibly parallel relationship. Such towbundles or like assemblages may oftentimes be of considerable magnitude.It is not unusual, for example, in the manufacture of, say, 1 to denierproducts, to

encounter tow bundles that are comprised of from 10,000 or 50,000 to200,000 or more individual component endless or continuous filaments.

.One of the serious problems encountered when aquagel fibers are beingprocessed in the indicated manner is the tendency of individualfilaments to adhere or stick to one another. Such behavior causescoarse, bonded ribbons to be formed which have many undesirablecharacteristics and which introduce many disadvantages. welded to oneanother generally suffer from a'hard hand, lumpy feel, stiffness, lackof luster and other deficiencies tending to cause their quality astextile products to be other than premium.

A major cause of fiber sticking inaquagel filaments is thought to be thehigh surface tension that existsbetween the wet surfaces of adjacentfilaments. Such surface tension exerts a considerable bonding forcebetween adjacent fibers. Other causes which contribute to sticking ofaquagel filaments are. the particular chemical.

stage processing of the material which would not occur.

in its handling in a dried condition. A

:Problems of interfilamentary sticking and bonding commonly occur inspinning, washing and. stretching operations during the manufacture ofvarious synthetic fibers produced by diverse wet spinning techniques.Many additives, usually referred to and known as being opening agents,have been employed to prevent the adhesion of individual filamentsduring processing. In the usual early stages of spinning, washing andstretching, the typical opening agent additives that have been utilizedare oil emulsions or surface active materials, or both, which areeffective to a greater or lesser extent to prevent interfilamentarywelding during fiber to fiber I contact in the processing. Agents ofthis general .variety are also sometimes referred to as lubricants.

In the manufacture of wet spun acrylonitrile polymer fibers by thereferred-to aquagel process in which aqueous saline solvents areemployed, the problems of interfilament adhesion in spinning andstretching stages are not of particular consequence and, prior to finalwashing before drying of the aquagel yarn, can be handled quite nicelyin the conventional manner. With such filaments, however, the stickingand interfilament bonding problem is severe and exceptionally seriousduring the hot air drying of intermediate aquagel product to the finallyobtained, irreversibly dried, hydrophobic yarn structure.

It would be of considerable advantage to provide opening agents whichwould be satisfactorily effective to prevent interfilamentary bondingand sticking together of individual yarn strands during theirreversibly-drying.

in hot air of acrylonitrile polymer aquagel fibers.

Therefore, it is the. principal object of the present in? vention toprovide new and improved opening agents? for acrylonitrile polymeraquagel fibers effective upon and for the irreversible drying of suchaquagel structures to a characteristically hydrophobic, synthetic tex-'of the'present invention, will be manifest in the following descriptionand specification.

. The present invention relatesto a significant improvement in theprocess of irreversibly drying an acrylonitrile polymer aquagel fiber,or an aquagel structure based essentially on an acrylonitrile polymer(particularly polyacrylonitrile), to the. finally dried,characteristically hydrophobic, synthetic textile fiber form desired.According'to the invention, the improvement consists ofimpregnating awet spun and washed and, advantageously, stretched (i.e., at leastpartially, if not completely, oriented) acrylonitrile polymer aquagelfiber prior to its final irreversible drying in hot air with an aqueoussolution of a chemical opening agent which consists of a compound,ormixture of compounds, from the class of ditertiary acetylenic glycolscharacterized in having any of the general structures:

wherein each R is independently an alkyl radical containing from 1 toabout 4 carbon atoms; and each Y is independently a cyclizing linearpolymethylene unit of from 4 to carbon atoms (i.e., tetramethylene orpentamethylene) which, together with the completing carbon atom to whichit is biterminally afi'ixed, forms an alicyclic ring system containing atotal of 5-6 carbon atoms. Advantageously, the acetylenic glycol that isemployed is 4,7-dimethyl-5-decyne-4,7-diol (commercially available fromthe Air Reduction Chemical Company as Surfynol 102) wherein, in FormulaI, each R is n-propyl. Other beneficial acetylenic glycols that may beutilized in the practice of the present invention are the typicalspecies set forth in the following Table I.

Chemical structures:

Key R Proper Name 1 Methyl 2,5-dimethyl-3-hexyne-2,S-dlol.

2 Ethyl 3,t}dimethyl-e-octyne-b,fi-diol.

3 N-propyl 4,7-dimethyl-5-decyne-4,7-diol.

4 lsobutyl 2,4,7,9-tetrarnethyl-5-decyne-4,I-diol. 5 See Structure below1,1-ethynylene-dicyclohexenol.

NOTE (8.) of the structure:

In general, the acetylenic glycols are very soluble in acetone, carbontetrachloride, ethylene glycol, ethyl acetate, methyl ethyl ketone andthe like; moderately soluble in benzene, cyclohexanone, ethanol,diethylene glycol, petroleum ether and the like; slightly soluble inkerosene; and insoluble in such solvents as mineral oil, soya bean oiland the like. The opening agents utilized in the practice of the presentinvention generally produce aqueous solutions or suspensions havingsurface tensions of less than about 50 dynes per square centimeter; aresuificiently water-insoluble to permit their presence as incompatibleoils with the fiber after the initial stages of drying (wherein a majorpart of the water present is removed) and during the critical finishingdrying stage, wherein the majority of sticking and interfilamentarybonding occurs; impart a non-adhesive film to the surface of theacrylonitrile polymer fiber that is treated (even when nitrile alloyfibers are involved, i.e., of the type containing polyvinyllactamadjuvants or other watersoluble or, at least, hydrophilic polymericingredients as dye-assistants); and are capable of being efl'icientlyand effectively removed near the end of the drying under the indicatedconditions so as to eliminate the possibility of their chemical reactionwith the fiber base and to avoid other undesirable consequences. Suchfeatures and characteristics secure for the acetylenic glycols thecapability of being quite advantageously utilized as fugitive openingagents in the practice and for the purposes of the present invention.They possibilitate a most satisfactory and beneficial effect.

The acetylenic glycol opening agents of the present invention areapplied to the intermediate aquagel 'fiber (0r tow bundles thereof)which has been prepared by wet spinning techniques using aqueous salinesolutions to prepare the polymer dissolving spinning solutions as wellas the coagulating baths therefor. The opening agent is applied afterthe aquagel has been washed completely or substantially completely fromresidual salt and, either concurrently with or subsequent to hotstretching for purposes of orientation of the aquagel fiber product. itis generally most convenient to apply the agent after stretchorientation and to make the application from a flushing bath, whereinthe residual moisture or water content in the aquagel fiber is replacedby the applicating solution or dispersion of the acetylenic glycolopening agent. 01": course, as has been indicated, it is most expedientto employ the opening agent on the aquagel fibers in tow bundle form.

Thus, for purposes of further particnlarization, the opening agents ofthe present invention are applied to strandular, filamentary and thelike aquagel structural forms of fiber-forming polymers that are basedupon acrylonitrile. These hydrated forms of the polymer, as is wellknown, may be obtained by extruding a spinning solution of the polymerinto an aqueous coagulating bath wherein the spinning solvent in theextruded filamentary structure is replaced to a large extent with water.Such water swollen or hydrated filamentary structures, as has beenindicated in the foregoing, can advantageously be prepared by extrudingsolutions or other spinnable dispersions of the fiber-formingacrylonitrile polymers in polyacrylonitrile-dissolving aqueous salinesolvents into aqueous, non-polymer-dissolving coagulating spin bathsolutions of the same salt or salts as used in the spinning solution.Advantageously, zinc chloride or its saline equivalents for such purposeare utilized, including such salts as calcium and other thiocyanatcs (asdisclosed in US. Patents Nos. 2,140,921 and 2,425,- 192), lithiumbromide, salts of the so-called lyotropic" series (as disclosed in US.Patents Nos. 2,648,592; 2,648,593; 2,648,646; 2,648,648, and 2,648,649),and saline equivalents thereof. Although it is desirable for the amountof water that is in the aquagel to at least gravimetrically equal thehydrated polymer that is contained therein, it may oftentimes bepreferable for the water to polymer weight ratio in the aquagel to be inthe neighborhood of from about 1.5:1 to 2.0:1, respectively. Aquagelstructures in which the water to polymer ratio is as high as 2.5 or 3:1and higher may also be satisfactorily employed.

The aquagel fibers that are treated with the acetylenic glycol openingagents in the practice of the present invention which are basedessentially on fiber-forming acrylonitrile polymers may be the usualhomopolymer or copolymer compositions containing in the polymer moleculeat least about percent by weight of acrylonitrile that are adapted toprovide the variety of filamentary products that are convenientlyreferred to as being acrylic fibers. Or, the basic acrylonitrile polymercomposition may contain or have other beneficial. additament ingredientsincorporated or combined therein. These may be the typical pigments,delusterants, textile assistants and the like (including antistaticagents) or they may be dye-assisting adjuvant materials. Thus, minorproportions (generally less than about 20 percent and frequently betweenabout 1 and 15 percent, of the dry weight of the fiber) of certaindye-receptive polymers may be incorporated in a polyacrylonitrile orother acrylonitrile polymer aquagel fiber that is treated in accordancewith the present invention. The dyereceptive polymers may be vinyllactam polymers, including poly-N-vinyl-2-pyrrolidone,poly-N-vinyl-Z-caprolactam, and the like; N-vinyl-2-oxazolidinonepolymers, in-

cluding poly-N-vinyl-Z-oxazolidinone, poly-N-vinyl-S-methyl-Z-oxazolidinone and the like; poly-N-vinyl-3 ZQQSAQQinorpholinone and the like; and more or less equivalent polymericdye-assistant adjuvants. The dye-assisting adjuvant materials of nitrilealloy type fibers may also be present in the essential acrylonitrilepolymer base in the form of graft or block copolymerized units of suchpolymers upon an already formed acrylonitrile polymer base or,alternatively, polymeric products in which the essential acrylonitrilepolymer base is graft or block copolymerized on an already formeddye-assisting adjuvant polymer backbone. It is generally preferred, forpurposes of terminological classification, to characterize the latter,highly advantageous variety of dye-receptive fibers as being nitrilealloy fibers in order to clearly distinguish them from the conventional,prototype, socalled acrylic fibers that were first known to the art. Theapplicating bath of the acetylenic glycol opening agent may be either awater solution or colloidal suspension thereof containing from about 0.1to 1.3 percent, and preferably at least about 0.4 percent, of dispersedactive agent. It is generally desirable for the acetylenic glycolopening agents to be formulated in the applicating compositions thereofas saturated solutions, i.e., in aqueous dispersions wherein theirconcentration is not in excess of that at which they form true solutionsor colloidal suspensions. Such manner of employment beneficially avoidsthe deposition of large oily particles on the aquagel fibers beingtreated, which might tend to produce non-uniform effects in thetreatment. Advantageously, the bath imparts between about 0.75 to 2.5percent by weight on the Weight of the dry fiber (o.w.f.) of the openingagent on the aquagel fiber. While it is advantageous to apply theopening agent from an impregnating bath, suitable results may also beachieved by spraying, rolling or wiping (as with wick applicators) theapplicating solution of the opening agent on the aquagel fibers beingtreated.

It is generally advantageous to apply the opening agents to the aquagelfibers or tow bundles thereof prior to any wet-crimping operation thatmay be contemplated for the fibers, if and when such operation isincluded in the processing sequence. Following the application of theopening agent, the aquagel fibers are irreversibly dried, to provide thedesired, characteristically hydrophobic, synthetic textile fiberproduct. Drying is best accomplished in and with hot air at temperaturesbetween about 100 and 150 C. for periods of time between about 30 andminutes. Fibers treated and dried in accordance with the presentinvention may generally be obtained in excellent finished form. Theyhave substantially, if not completely, reduced occurrence of undesiredsticking and interfilamentary bonding and are in a condition wherein theoptimum properties of the fiber product is brought out to bestadvantage.

One peculiar and distinctively beneficial advantage of the acetylenicglycol opening agents that are, employed in the practice of the presentinvention lies in their ability to be successfully and satisfactorilyrecovered for re-use after their application in the process. As isevident in the foregoing, the aquagel tow bundle entering the dryingovenor chamber can be shown to contain the agent. However, the irreversiblydried fiber product leaving the drying area contains none or vanishinglysmalland insignificant quantities of the agent. This is experienceddespite the fact that successful opening action has been accomplishedand the agent has operated in the desired manner during the drying step.It is believed that the agent is removed from the aquagel structurebeing dried by means of steam distillation. Thus, recovery of thecondensate and re-use of the agent is an attractive feature of thepresent invention. Of at least as great importance is the fact that, dueto the fugitive and nonresidual character of the acetylenic glycolopening agents, they are absent from the finally dried fiber, thus avoiding any possibility for interfering with subsequent processingoperations and normal usage of the textile proda net. -In'-this way,fibers preparedfollowing' the practice of the present inventionexperience no decrease in heat or light stability, luster or dyeability.They have a completely dry and non-oily hand, and are not subject tobeing tacky or otherwise altered due to the presence of residual openingagent on their surfaces.

' The invention is further illustrated in and by the following exampleswherein, unless otherwise indicated, all parts and percentages are to betaken by weight.

Example 1 A polyacrylonitrile spinning solution was prepared bydissolving about one part of a fiber-forming species of the polymerhaving an average molecular weight between about 30 and 35 thousand inabout 10 parts ofa percent aqueous solution of zinc chloride. The"spinning solution had a viscosity of about 2200 poises at a temperatureof about 25 C. It was extruded at about 30 C. through a spinnerettesystem into about 15 thousand separate, individual aquagel filaments.The diameter of each jet hole through which each individual 'filamentwas extruded was about 6 mils. The extruded spinning solution wascoagulated in a coagulating liquid comprised of about a 43 percentaqueous solution of zinc chloride at 15 C. The aquagel filaments werewithdrawn from the coagulating liquid and assembled in the form of arelatively flat, ribbon-like, multiple filament tow bundle. The wet spuntow was then passed into a water wash bath, wherein it was washed to thepoint at which the zinc chloride content was not in excess of about 0.05percent. The washed tow was then oriented by being stretched to a totallength of about 12 times its original length. By these operations therewas obtained a washed and oriented filamentary tow bundle of the 15,000individual aquagel strands. The total aquagel denier of the washed andoriented tow bundle was about 100,000. The tow bundle had an averagewidth of about one inch and an average thickness of about 20 thousandthsof an inch. The oriented aquagel structures contained about 2.0 parts ofwater for each partof fiberforming polya crylonitrile that was presenttherein. In addition, the aquagel contained about 8 percent of poly-N-vinyl-2-pyrrolidone (PVP) (based on the dry weight fiber) that hadbeen incorporated therein as a polymeric dye-assisting adjuvant byimpregnation of the watersoluble polymer (from an impregnating bath inwhich it was contained in aqueous solution) into the aquagel structure.

. The washed and oriented tow was then passed in a.

relaxed state onto a continuous belt drier and driedin hot air at 150"C. for about 15 minutes to achieve the irreversible drying and convertthe aquagel to the final,

' 3 denier per filament, characteristically hydrophobic,

synthetic textile fiber structure. The tow bundle was then tested by astandard method of analysis to determine the. number of sticks per gramin the finally obtained product. The analysis method employed is onecommon and well known to the art, wherein a card web of the, fiber isobserved in order to count neps or blemishes therein. A segment ofcarded web fiber is visually examined after a specified number of passesthrough a sample card. Sticks per gram are an expression of the numberof bonded fibers 'counted on a standard sample. Two passes through thesample card arefound to approximate the standard cotton cardingoperation performed'on a production scale. The sticks observed aftersuch treatment provide an accurate picture orrepresentation of thefrequency or number of bonded fibers present. The change in sticks ornumber of bonded fibers present after four passes of the fiber samplethrough a sample card give a measure of the severity of bonding. Itshould benoted, incidentally, that there is no sig-"' nificantdilference in the test method between measures of say, 0 and 4 sticksper gram. Such values are 'essen-.--

tially the same within the accuracy of the examination procedure used.The untreated tow bundle was found to have been prepared with about 280sticks per gram after the second pass over the card web and with about38 sticks per gram after the four passes over the sample card.

In contrast with the foregoing, the spinning and drying procedure wasrepeated on three additional tow bundle samples excepting that,immediately prior to drying the washed and stretched tow bundles, theywere passed through an aqueous applicating solution of an acetylenicglycol opening agent in accordance with the practice of the presentinvention at room temperature with a two second residence (immersion)time of each tow bundle sample in the bath. Each of the treating bathsemployed had a different concentration of the opening agent therein. Thetreated tow bundle was not rinsed prior to drying. The acetylenic glycolemployed was 4,7-dimethyl--decyne-4,7-diol (Surfynol 102). The resultsare set forth in the following tabulation, wherein the untreated controlsample (sample A) referred to in the foregoing is included forcomparative purposes and the quantity of the acetylenic glycol employedin the separate treating baths for each of the treated samples B, C andD is also indicated.

By way of additional contrast with the foregoing, an aquagel 3 denierper filament tow bundle prepared in the same way as above described wasdried in a completely relaxed state and without opening agent treatmentto obtain the final synthetic fiber structure. The procedure wasduplicated excepting to soak an identical wet tow in a 0.4 percentaqueous solution of Surfynol 102. After drying, each tow bundle wasdipped into a 1 percent solution of Emulphor EL-719 (a syntheticdetergent consisting of a nonionic acyl (fatty) polyoxyethylene glycolsupplied by General Aniline & Film Corporation), squeezed, and againdried for 10 minutes in a 150 C. oven. The Emulphor is a standardfinishing agent used for antistatic and lubricating purposes for thefinally dried product. It is not an opening agent. The product treatedwith opening agent had 219 sticks per gram. The untreated tow, by way ofcomparison, was found to contain about 389 sticks per gram.

The same results were obtained when the foregoing procedure wasidentically duplicated excepting to omit application of the EmulphorEL719 to the tow bundles.

Example 3 An aquagel tow bundle was prepared identically as in Example 1with the major exception that no PVP was incorporated in thepolyacrylonitrile fibers. The tow bundle, prior to drying, was treatedwith Surfynol 102 in the same way as in the first example. The dried,treated tow bundle was exceptionally open and flufiy. Its individualcomponent filaments were distinctly individal and non-bonded. in markedcontrast therewith, an identical polyacrylonitrile aquagel tow bundlethat was dried without being treated in accordance with the presentinvention had a significantly inferior and undesirable shredded wheat"fibrous appearance and feel.

Example 4 Similar results are obtained when the foregoing is repeatedexcepting to use other forms and types of unmodified polyacrylonitrileor to employ unmodified acrylonitrile copolymer fibers or when usingnitrile alloy fibers containing other polymeric dye-assisting adjuvantsin place of the poly-N-vinyl-2-pyrrolidone, such as poly- N vinyl 2oxazolidinone, poly N vinyl 5 methyl 2 oxazolidinone, poly N vinyl 3morpholinonc, etc. Analogous excellent results are also obtained whenusing either Surfynol 82 or Surfynol 104 as the opening agent, as wellas any other of the acetylenic glycols specifically illustrated in TableI or fitting within the scope of the Formulae I, II and III.

The scope and purview of the invention is to be gauged in the light ofthe hereto appended claims rather than strictly from the decentembodiments that have been set forth in the foregoing description andspecification.

What is claimed is:

1. In the method of irreversibly drying an acrylonitrile polymer aquagelfiber to convert it to a synthetic, characteristically hydrophobic,textile fiber product, said aquagel consisting essentially of anacrylonitrile polymer that contains at least about weight percent ofacrylonitrile polymerized therein, any balance being another polymerizedmonoethylenically unsaturated monomer that is copolymerizable withacrylonitrile, said aquagel containing between about 1 and 3 parts byweight of hydrated water to each part of dry polymer therein, theimprovement which consists of applying to said aquagel fiber prior todrying between about 0.75 to 2.5 percent based on the weight of theaquagel fiber, of an acetylenic glycol opening agent selected from theclass consisting of those having the structural formulae:

wherein each R is independently an alkyl radical containing from about 1to 4 carbon atoms; and each Y is a cyclizing linear polymethylene unitwhich, together with the completing carbon atom to which it is aifixed,forms an alicyclic radical of from 5 to 6 carbon atoms; thenirreversibly drying the aquagel in hot air at a temperature betweenabout and C. for a period of time between about 30 and 5 minutes.

2. The method of claim 1, wherein said opening agent is applied to saidaquagel fiber from an applicating aqueous bath of said agent containingbetween about 0.1 and I 1.3 percent by weight, based on the weight ofthe bath,

of said opening agent dispersed therein.

3. The method of claim 2, wherein opening agent is applied by immersingsaid fiber in said applicating bath.

4. The method of claim 1, wherein said aquagel fiber is treated anddried while it is assembled in tow bundle form. 1 a 1 5. The method ofclaim 1, wherein said aquagel fiber is a polyacrylonitrile fiber. I

6. The method of claim 1, wherein said aquagel fiber is a nitrile alloyfiber which consists essentially of a composition of (1) at least about80 weight percent,

based on the dry weight of the composition, of an acrylonitrile polymerthat contains at least about 80 weight percent of polymerizedacrylonitrile therein, any balance being another polymerizedmonoethylenically unsaturated monomer that is copolymerizable withacrylonitrile, and (2) up to about 20 weight percent, based on the dryweight of the composition, of a polymerized dyeassisting adjuvantselected from the group consisting of polymerized N-vinyl-2-pyrrolidone,polymerized N-vinyl- 2-caprolactam, polymerized N-vinyl-Z-oxazolidinone,polymerized N vinyl 5 methyl 2 oxazolidinone and polymerizedN-vinyl-3-morpholinone.

7. The method of claim 6, wherein said nitrile alloy fiber is comprisedof polyacrylonitrile containing intimately blended therewith up to about20 percent by Weight, based on the dry weight of the fiber, of poly-N-vinyl-Z-pyrrolidone as a dye-assisting adjuvant.

8. The method of claim 1, wherein said opening agent is4,7-dimethy1-5-decyne4,7-diol.

9. The method of claim 1, wherein said opening agent is3,6-dimethyl-4-octyne-3,6-diol.

10. The method of claim 1, wherein said opening agent is2,4,7,9-tetramethyl-5-decyne-4,7-diol.

11. The method of claim 1, wherein said opening agent is2,5-dimethyl-3-heXyne-2,5-diol.

12. The method of claim 1, wherein said opening agent is1,1'-ethynylene-dicyclohexanol.

References Cited in the file of this patent UNITED STATES PATENTS

1. IN THE METHOD OF IRREVERSIBLY DRYING AN ACRYLONTRILIE POLYMER AQUAGELFIBER TO CONVERT IT TO A SYNTHETIC, CHARACTERISTICALLY HYDROPHOBIC,TEXTILE FIBER PRODUCT, SAID AQUAGEL CONSISTING ESSENTIALLY OF ANACRYLONTITRILE POLYMER THAT CONTAINS AT LEAST ABOUT 80 WEIGHT PERCENT OFACRYLONITRILE POLYMERZIED THEREIN, ANY BALANCE BEING ANOTHER POLYMERZIEDMONOETHYLENCIALLY UNSATURATED MONOMER THAT IS COPOLYMERIZABLE WITHACRYLONTIRILE, SAID AQUAGEL CONTAINING BETWEEN ABOUT 1 AND 3 PARTS BYWEIGHT OF HYDRATED WATER TO EACH PART OF DRY POLYMER THEREIN, THEIMPROVEMENT WHICH CONSISTS OF APPLYING TO SAID AQUAGEL FIBER PRIOR TODRYING BETWEEN ABOUT 0.75 TO 2.5 PERCENT BASED ON THE WEIGHT OF THEAQUAGEL FIBER, OF AN ACETYLENIC GLYCOL OPENING AGENT SELECTED FROM THECLASS CONSISTING OF THOSE HAVING THE STRUCTURAL FORMULAE: